All of the US economy's problems come back to one thing

The rough patches and disappointments that are plaguing the US economy are all symptoms of one thing, according to Tim Hopper of TIAA Global Asset Management: the slack left in the labor market.

For instance, the chief economist said, the downturn in capital spending by businesses and the declining productivity of workers has to do with the ability of businesses to hire workers at a lower cost than it would be to buy physical assets.

"One way to improve productivity is to buy better equipment that makes workers more productive," Hopper told Business Insider. "The problem is, with low wage growth and continued labor market slack, it's cheaper for businesses to just hire a new person instead of making that big investment."

Essentially, with more Americans willing to take a smaller paycheck to get a job, the cost of labor is cheap compared with that of large equipment.

Hopper said that while there had been strong headline gains in July's monthly jobs report, the fact that wages were still growing slower than before the recession and that people were entering the workforce directly to employment shows there is more room to grow.

The low inflation that has been a significant thorn in the side of the Federal Reserve is also a symptom of the continued weakness in the job market.

"Wages and inflation are connected by the Phillips curve," Hopper said. "So the slower wage gains post-financial crisis are making it nearly impossible to deliver the kind of inflation the Fed wants."

Hopper also said the records being set in job openings were indicative of the same good-but-not-great labor environment.

"The labor force has grown in terms of raw numbers, so you would expect new records in job openings simply as a symptom of a bigger economy," Hopper said. "It's actually telling that we're not setting records consistently and by a larger margin."

All in all, a lot of the problems that are nagging the US economy, even the lower-than-desired gross-domestic-product growth, can trace their roots back to the labor market.

"Shoring up the health of the labor market is core to getting us back on track," Hopper said. "That's what you have to focus on to fix everything else."